This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We appreciate the comments on the renewal application for MRAC MCB060027, A combined computational and experimental study on the ligand - gating in CNG and HCN channels, by Lei Zhou and Steven A. Siegelbaum. We found that most of the comments from both anonymous reviewers were very constructive and helpful for us to further improve the original proposal. As quoted in the Proposal Comments by Allocation Staff, one of the major technical concerns by reviewer 1 is on the weakness in the application of TI. Actually we had carried out the TI almost exactly as described by reviewer 1 (first removing electrostatic and then VDW interactions;comparing the difference between removing ligand from protein and versus removing it from bulk solvent). However, we were concerned with the file size (already 15 pages) so that we didnt present all the technical details or preliminary results in the renewal application. Here we carefully address concerns raised by both reviewers and add those technical details together with the related preliminary data. We hope that this response together with the original renewal application will satisfy these concerns and enable this proposal to be found acceptable so that we may continue the research proposed in this MRAC renewal application. Thank you for your consideration.